Silver halide emulsion containing a thio-imino-urazole as a stabilizer



atented Mar. 25 1952 SILVER HALIDE EMULSIQN CONTAINING A THIO-I-MINO-URAZOLE AS A STABILIZEB John David Kendall and Douglas James Fry, more. England, assignors to Ilford Limited, Il or Eng and, a. British com ny No Drawing. Application April 11, 1950, Serial No. 155,356. In Great Britain April 11, 1949 12 Claims. (01. 95-4) This invention relates to compounds hi when ncl ded a photogra hi sil er hal de emulsion la or in a or l er p e en in a Photographic mate a includin such e niilo e r o he develo erl f or o other processing bath applie t the. photo ra ic m terial, improve the. qual ty of the de elop d hotographic ima es ob a n d- In the production of photo aph c ima n silver halide emulsions, and particularly in the case of emuls ns n when the sil er ha i e is predominantl silver chi id the maximum mage density obt inable is not always so re t as m y be desire Moreover, the com on p actice of hot-glazin photo raphic p ints. tends to affect adversely the image olour ivin a p o qua ty ack hav ng a bronzed appearance, and also reduces the eiiective maximum density obtainable in the image.

It has now been discovered that this bronzing efiect may be reduced or eliminated and the maximum d ty obt ina le may be nc e ed b bringing into contact with the photographic emuls o a m mber or a certa n c as o het r cyc nitrogen compounds, and according to this invention, therefore a method of improving photoh c silver h e e lsions n r ga d to the quality of the images developed therein comprises applying to such emulsions, e. g. by including in the emulsion, or in another layer of the photo.- graphic element containing such emulsion, or in a developing, fixing or othe ocessing bath with wh h the photographic elem nt s t ea e a heterocyclic compound of the general rormula:

where R is a hydrogen atom or a hydrocarbon group.

The said compounds may be defined as 3-thio- 5-iminourazoles and may be prepared by well k w methodso examp the compound in which R is a hydrogen atom may be prepared by the method described in Liebigs Annalen der Chemie, volume 426, at page 313, and the compound where R is a phenyl group may be prepared by the method described in Berichte der Deutschen Chemischen Gesellschaft, volume 55, at page 12. These two compounds are the preferred compounds for use in the present invention, but the invention also includes the use of compounds where R represents other hydrocarbon groups, e. g. alkyl. such as methyl, ethyl and higher alkyl, aralkyl, such as benzyl, and other aryl groups. such as naphthyl.

a superecoat layer.

The compounds may be used as free bases or as ammonium or alkali metal salts. They may also be used in the form of their substantially water-insoluble colourless metal derivatives, said metal derivatives being soluble or decomposible during treatment of the photographic element with processing baths subsequent to the development of the element. Such metal salts may be silver or nickel or other metal mentioned in British Specification No. 573,745 to which reiere once is made for details of this aspect of the invention. V

As already indicated these compounds may be included in the silver halide photographic emulsion or in another layer of the photographic element, preferably coated adjacent to such emulsion layer, for example in a sub-coat layer or in The optimum quantity of compound to be employed will always be small, but will depend on the particular substance selected. In general it is found that for incorporation in an emulsion, sub-coat or super-coat, a proportion of 1 part of the compound in 1000. to 900 o t e emu s u e t or S bsolution is generally suitable, While for incorporas tion in a developer, fixer or other treatment bath, e. g, a glazing solution, the optimum quantity may be, ior'example, between 1 part in 300.0 to 1 part in 300,000 parts of the processing so1ution. Frequently even lower concentrations than those given above have some effect and, though it may be uneconomic in being a waste of material, even higher concentrations may be employed.

More than one compound of the type defined may be used if desired, and the compound or compounds may be used in more than one way, e, g. in super-coat and developing solution, or in both developing and fixing solutions.

Mixtures of the compounds with any of those specified for similar use in British Specifications Nos. 573,745 and 583,648 may also be employed.

In general the compounds will be applied to the photographic emulsion before reaching the final stage of drying the developed image, but they may be applied with advantage to already dri d pr nt w r it is e red o sub c e latter to hot-glazing. V a

The following examples illustrate the invention:

Example 1 To a gelatin super-coat solution was added a solution of 3-thio-5 -iminourazole in the proportion of 1 part of the compound per 5000 parts of the gelatin solution by weight. This supercoat was applied over- (A) A silver chloride photographic emulsion of the type known as vigorous gaslight.

lglaxiltnunli lvflaximtum ensl y ms y Emulswn (A 15) cold-dried after hot coatings glazing Control A 1.84 1.50 Test A 1.87 1.95 Control B.-. 1.90 l. 65 Test B 1. 94 2.01

Example 2 A silver chloride photographic printing paper of the type known as vigorous gaslight was exposed and developed in a standard metolhydroquinone developer, fixed, washed and hotglazed. Small quantities of 3-thio-5-phenyliminourazole were added to the developing bath and, in a second test, to the acid fixing bath, and the following results were obtained.

- Maximum Test gy elq 8335 A i a non a at o addition glazing Control None None 1.41 A lpart per do 2.02

1,000. B None One part 1.76

per 10,- 000.

What we claim is:

1. A method of improving photographic silver halide emulsions in regard to the quality of the. images developed therein which comprises developing such emulsions in a developing bath which contains a small quantity of 3-thio-5- phenyliminourazole.

2. A method of improving photographic silver halide emulsions in regard to the quality of the images developed therein which comprises developing such emulsions in a developing bath which contains a small quantity of 3-thio-5- iminourazole.

3. A method of improving photographic silver halide emulsions in regard to the quality of the images developed therein which comprises developing such emulsions and thereafter fixin the emulsions in a fixing bath containing a small quantity of 3-thio-5-phenyliminourazole.

4. A method of improving photographic silver halide emulsions in regard to the quality of the images developed therein which comprises developing such emulsions and thereafter fixin the emulsions in a fixing bath containing a small quantity of 3-thio-5-iminourazole.

5. A photographic element which includes a silver halide photographic emulsion layer and in contact therewith uniformly throughout, a small quantity of a heterocyclic compound of the general formula:

.where R is selected from the class consisting of the hydrogen atom and hydrocarbon groups.

6. A photographic element which includes a silver halide photographic emulsion layer and in contact therewith uniformly throughout, a small quantity of 3-thio-5-phenyliminourazole.

7. A photographic element which includes a silver halide photographic emulsion layer and in contact therewith uniformly throughout, a small quantity of 3-thio-5-iminourazole.

8. A photographic element which comprises a silver halide photographic emulsion layer and coated adjacent thereto a water-permeable colloid layer which contains a small proportion of 3-thio-5-phenyliminourazole.

9. A photographic element which comprises a silver halide photographic emulsion layer and coated adjacent thereto a water-permeable colloid layer which contains a small proportion of 3-thio-5-iminourazole.

10. A method of improving photographic silver halide emulsions in regard to the quality of the images developed therein which comprises treating such emulsions with photographic processing baths in the presence, at least at one stage in the processing, of a heterocyclic compound of the general formula:

where R is selected from the class consisting of the hydrogen atom and hydrocarbon groups.

11. A method of improving photographic silver halide emulsions in regard to the quality of the images developed therein which comprises treating such emulsions with photographic processing baths in the presence, at least at one stage in the processing, of a small quantity of 3-thio-5- phenyliminourazole.

12. A method of improving photographic silver halide emulsions in regard to the quality of the images developed therein which comprises treating such emulsions with photographic processing baths in the presence, at least at one stage in the processing, of a small quantity of 3-thio5- iminourazole.

JOHN DAVID KENDALL. DOUGLAS JAMES FRY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date I 1,560,240 Jelley Nov. 3, 1925 2,298,093 Dersch Oct. 6, 1942 2,363,493 Baldsiefen Nov. 28, 1944 

2. A METHOD OF IMPROVING PHOTOGRAPHIC SILVER HALIDE EMULSIONS IN REGARD TO THE QUALITY OF THE IMAGES DEVELOPED THEREIN WHICH COMPRISES DEVELOPING SUCH EMULSIONS IN A DEVELOPING BATH WHICH CONTAINS A SMALL QUANTITY OF 3-THIO-5IMINOURAZOLE.
 5. A PHOTOGRAPHIC ELEMENT WHICH INCLUDES A SILVER HALIDE PHOTOGRAPHIC EMULSION LAYER AND IN CONTACT THEREWITH UNIFORMLY THROUGHOUT, A SMALL QUANTITY OF A HETEROCYCLIC COMPOUND OF THE GENERAL FORMULA: 